This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-269261, filed Sep. 22, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a fixing device for an image-forming apparatus, and in particular, to a fixing device for an electrophotographic apparatus where induction heating is employed as a heating source.
According to the conventional fixing device of electrophotographic apparatus, the fixing is generally performed as follows. Namely, a halogen lamp is employed as a heating source, wherein the halogen lamp is disposed inside a metal roller to heat the roller, and an elastic roller is pressed onto the metal roller with a sheet-like material with an unfixed image (a material which is subjected to the fixing, such as paper) interposed therebetween, thereby press-contacting the sheet-like material onto the metal roller. These rollers are then rotated and the sheet-like material is passed through an interface between these rollers. Alternatively, a method of heating the roller in a non-contact manner by making use of a flush lamp is also put to practical use.
FIG. 1 schematically illustrates the en tire structure of the conventional fixing device. Namely, the fixing device for electrophotography is generally constituted by a heating roller 1 formed of a thin wall metal roller and housing therein a halogen lamp heater 2 as a heating source, and a pressing roller 3 having an elastic surface layer for bringing a sheet-like material into sufficient contact with the heating roller 1. These heating roller 1 and pressing roller 3 are supported by means of a pressing mechanism (not shown) so as to ensure a predetermined contacted width therebetween, and are also made rotatable by means of a driving source (not shown) so as to make the peripheral speed of these two rollers identical with the transferring speed of the sheet-like material.
According to the conventional fixing device of this system, since the heating roller is heated by making use of a lamp, the heat efficiency thereof is at most about 70%. Additionally, since the heating roller is constructed such that it is heated from the inside thereof, the heating roller is accompanied with various problems that the kick-off property of temperature is poor, that the structure thereof is rather complicated, and that it is difficult to miniaturize the heating roller.
With a view to improve the efficiency of the fixing device, there have been proposed a fixing device wherein a magnetic field-generating means is combined with a belt so as to utilize a induction heating (Japanese Patent Unexamined Publication H8-76620), and a fixing device wherein ceramics is employed as a heating member (Japanese Patent Unexamined Publication S59-33476).
Among these fixing devices, the fixing device which takes advantage of induction heating is defective in that, since the induction heating is incapable of realizing a uniform heating, a non-uniform temperature distribution would be generated on the surface of the roller, and due to this non-uniform thermal load, the roller may be damaged. If this problem is to be overcome, any member to which toner is more likely to adhere among the members which contact with the outer surface of the fixing roller is required to be heated prior to initiating the rotational movement of the fixing roller.
Further, for the purpose of optimizing the exothermic efficiency by optimizing the impedance, the construction of the coil is required to be optimized. The optimization of exothermic efficiency leads to the effect of saving the energy.
Meanwhile, according to the conventional fixing device where a halogen lamp is utilized as a heating source, the non-uniformity of temperature in the axial direction of the heating roller has been overcome by changing the light distribution property of the lamp. However, it is also required to cope with this non-uniformity of temperature even in the fixing device utilizing induction heating.
An object of the present invention is to provide a fixing device for fixing an image of developer (which is referred hereinafter to as a fixing device), which is capable of optimizing the exothermic efficiency, capable of uniformly heating the heating roller, and capable of being manufactured cheaply.
According to the present invention, there is provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; and the supporting member has a frame structure which is partitioned into a plurality of sections which are partitioned in a direction perpendicular to the transferring direction of the sheet-like member.
According to the present invention, there is also provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; and the coil member is constituted by a plurality of coil components which are connected with each other in such a manner that an electric voltage between a connecting terminal of a first coil component and a connecting terminal of a second coil component disposed next to the first coil component is smaller than an electric voltage between a connecting terminal of a first coil component and a connecting terminal of a third coil component disposed not neighboring to the first coil component.
According to the present invention, there is also provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; and the coil member is provided with a pair of lead wires for connecting it with a driving circuit for driving the coil member, said pair of lead wires being drawn out in one direction which is perpendicular to the transferring direction of the sheet-like member.
According to the present invention, there is also provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; and the coil member is constituted by a plurality of coil components which are connected with each other using a crimp-style terminal on one side in a direction perpendicular to the transferring direction of the sheet-like member, the connected portion of said coil components being undergone with an insulating treatment and bent inside said coil member.
According to the present invention, there is also provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; that the supporting member is provided with at least one tapering portion or step portion which is formed along a direction perpendicular to the transferring direction of the sheet-like member, and that the coil member is provided with at least one tapering portion or step portion which is formed in conformity with the tapering portion or step portion formed on said supporting member.
According to the present invention, there is also provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; and that the coil member is constituted by a plurality of litz wires which are designed to be altered in the manner of combination or of connection thereof, thereby enabling a plurality of different electric voltages to be applicable.
According to the present invention, there is also provided a fixing device comprising an endless heating member which is adapted to be moved at the same velocity as the transferring speed of a sheet-like member with an image thereon and is adapted to be contacted with the sheet-like member to thereby enable the image on the sheet-like member to be thermally fixed; and an induction heating mechanism for performing an induction heating of the endless heating member, wherein the induction heating mechanism comprises a coil member, and a supporting member for supporting the coil member; and the coil member has a central space, whose width is varied along a direction perpendicular to the transferring direction of the sheet-like member.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.